1. Field of the Invention
This invention relates to novel antitumor compounds of HP530 or their pharmaceutically permissible salts, processes for preparing them and antitumor compounds containing the HP530 compounds as their active ingredient.
2. Description of the Prior Art
Microorganisms are known to produce a variety of antitumor compounds having the features in their chemical structures in a broad range. Antitumor compounds belonging to the pluramycin group exhibiting a strong antitumor effect have been reported in some papers as, for example, pluramycin A (The Journal of Antibiotics, Series A, Vol. 9, pp. 75, 1956), neopluramycin (The Journal of Antibiotics, Vol. 23, pp. 354, 1970; Vol. 30, pp. 1143, 1977), kidamycin (The Journal of Antibiotics, Vol. 24, pp. 599, 1971), hedamycin (Helvetica Chimica Acta, Vol. 60, pp. 896, 1971), rubiflavins (Helvetica Chimica Acta, Vol. 63, pp. 2446, 1980; Vol. 70, pp. 1217, 1987), SS21020 compounds(Japanese Patent Kokai Koho No. 277682/1986), ankinomycin (The Journal of Antibiotics, Vol. 42, pp. 149, 1989), altromycin (The Journal of Antibiotics, Vol. 43, pp. 223, 1990), DC92-B (The Journal of Antibiotics, Vol. 43, pp. 485, 1990), and so forth.
Besides their peculiar activity, however, the conventional antitumor compounds involve generally the common problem in that they exhibit strong toxicity.